I think some (many?) parents don't understand how teaching works these days. It's not like when we went to school - time's have changed! And why would parents understand the changes? I didn't as a parent, but I do now I'm a teacher (2nd career).
I'm in primary, and if a child is frequently absent they will have gaps in their learning. So, for example, in teaching fractions in year 5, which can take a few weeks, they will have gaps if they are off. We don't have time to go back over it because we are trying to cram in so much stuff these days, as we need to deliver a full and rounded curriculum as requested by Govt. If your child is not in, then they will miss out that day's learning. We go over fractions again in yr6 but it's a recap to further embed learning and it's a much shorter session. I've got a child who missed it in yr5 because they were ill and then yr6 due to parents deciding a 2 week holiday was more important. Holiday was avoidable, illness was not. That child now is not on a par with their peers and finds maths tough as it is; they're very anxious about assessments because there's a whole bunch of questions they don't know how to answer.
What we have seen due to covid is that there are huge gaps for many kids. To use the analogy of building a house, if they don't have strong foundations, there'll be cracks and damage as the house is built.
If your child is ill (and I include mental health in that), then that can't be avoided. But if it's due to choice, then I can't understand why you would actively choose to continue to cause further damage to your child's (academic) education and effectively continue to weaken the foundations of your 'house'. As teacher's we're constantly told that we have loads of holiday (13 weeks) so it's not like there isn't time to cherish with family members and build memories and do the other side of education that isn't academic.
As for strikes, then no teaching is taking place, your child is not missing out in the same way, with gaps in their education, whilst their peers do not.